Electrically driven saws are generally used for removing plaster or resin type orthopedic casts on human limbs or appendages. A cut is made and then the cast is split for removal. The process itself is not pleasant for the patient. Pediatric patients are often intimidated by the sawing. The saws are noisy and usually produce much dust in the cutting operation.
The prior art shows an alternate method that involves the use of an embedded wire or strand which is attached to the surface of a patients limb prior to embedding in the cast itself. By pulling the wire through the cast, the cutting action will separate the cast for removal thereby avoiding the use of a saw with its noise and dust drawbacks.
Babka in his U.S. Pat. No. 3,867,931 describes a method for removing an orthopedic cast utilizing an embedded wire which is pulled through the thickness of the cast by manually operated ratchet apparatus. This tends to be a slow operation which also transfers substantial reaction force and torque to the patient during the removal process.
An improved wire cast cutting system is revealed in U.S. Pat. No. 4,227,517 of Aguiar. It involves the use of a battery operated device using a gear motor to pull the embedded wire at an acute angle through a low friction guide plate resting on the surface of the cast. This greatly reduces the jostling of the patient by the procedure since the pulling force is localized to the tool. The tool is grasped by the technician and moves along the cast as the cutting action progresses. A combination of large numerical gear reduction ratio and substantial motor power is required to perform the cutting operation at a timely rate. Both of these requirements indicate that the specially designed removal device drive head as well as its battery supply may be bulky and expensive. The wire pulling force must overcome any resistance as provided by the hardest and most difficult region of the cast encountered along the pulling path. The torque provided by the removal tool must match and overcome this worst-case resistance to prevent bogging down and stopping.